1. Field of the Invention
The present invention relates to a burn-in test for hybrid ICs equipped with semiconductor power elements such as power MOSFETs or the like mounted by bare chip mounting.
2. Description of the Prior Art
Conventionally, a hybrid IC is well known which has both a semiconductor power element such as a power MOSFET or the like and a control circuit for controlling the semiconductor power element mounted on the same substrate. To the substrate of the hybrid IC is mounted specifically a transfer-molded semiconductor power element or a bare semiconductor power element without being molded (referred to as bare chip mounted semiconductor element hereinafter).
The transfer-molded semiconductor power element can be subjected to a burn-in test before mounted to the substrate of the hybrid IC. On the other hand, in the case of the bare semiconductor power element without molded with a resin or the like, the burn-in test is conducted to the substrate of the hybrid IC after the semiconductor power element is mounted to the substrate.
In general, the control circuit to be mounted to the hybrid IC is often equipped with a protecting Zener diode for preventing a voltage not smaller than rated V.sub.GSS from being impressed between a gate and a source of the semiconductor power element. The protecting Zener diode acts not to apply a Zener voltage V.sub.Z or higher voltage (V.sub.Z &lt;V.sub.GSS is satisfied) to between the gate and source of the semiconductor power element. Therefore, the burn-in test of impressing a voltage exceeding the Zener voltage V.sub.Z to between the gate and source of the bare chip mounted semiconductor power element is practically impossible.
When the rated voltage V.sub.GSS of the semiconductor power element is higher than a rated voltage V.sub.CC of the control circuit, a voltage between the gate and source is required to be set so that the control circuit receives a voltage not higher than the rated voltage V.sub.CC.